Population forecast sees peak, decline

9 billion global figure is lower than other views

The world's population will rise to about 9 billion in the next 70 years and then will stop growing and start to decline, a group of demographers predicted Wednesday.

By 2100, it will fall back to 8.3 billion, they say.

The new study, published in the science journal Nature, bucks other predictions that foresee global population surging as high as 25 billion in 150 years.

"It gives us a different picture of the future, that there is no reason for this apocalyptic view of population explosion and the population breeding itself out. That is all on the mental level," said Wolfgang Lutz, of the International Institute for Applied Systems Analysis in Austria, who is the main author of the study.

The findings suggest that it is not an apocalypse but cultural changes around the globe that will turn around population growth.

"The future of population does not come out of a computer but comes out of billions of beds of real people at night," said Joel Cohen, professor of population studies at Rockefeller University in New York.

China, with its population of more than 1 billion, experienced an extraordinary decline in fertility during the last few decades. Because of modernization and improvements in health, population decline was already in effect even before China's One Child Policy.

South Asian countries, such as India and Pakistan, whose populations rival China's, are also undergoing a fertility decline, though not as quickly.

One region of extremely slow decline is Africa. Despite the high mortality from AIDS, in 2050 Africa will have three times the population of Europe, the researchers foresee. Today it is about the same as Europe, about 800 million.

If not for the higher fertility rates among immigrant and minority populations, the population of the U.S., currently 285 million, would not reach replacement levels.

The 20th Century witnessed an extraordinary growth in world population, from 1.6 billion to over 6.1 billion today. In 1960 the world population was 3 billion, so those who are older than 40 today have experienced a doubling of the world population, a unique event in world history.

But as world population growth comes to a halt, there will be a tremendous shift from a youthful population (lots of people under 15) to an elderly population (lots of folks older than 60). By 2100, 40 percent of the North American population will be elderly, up from 16 percent. Demographers agree that countries without adequate social security programs will be tremendously affected.

The graying of the world will be seen most starkly in Japan, where every other person will be 60 or older by 2100, according to Sergei Scherbov, co-author of the study.

Lutz also predicts that the world will divide between countries with shrinking populations and those with growing populations, and tensions will rise over immigration.

The new estimate is similar to projections up to 2050 by the United Nations, U.S. Census Bureau--International Division and the Population Reference Bureau. After that, however, the projections diverge. The UN estimate puts the world population at 10 billion by 2185 without any decline.

On Wednesday, the UN's demographers stood by their estimates, saying that that the new study is overly simplistic. The Austrian team divided the world into 13 regions; UN calculations were based on fertility rates in 224 countries.

"What we do is a massive undertaking. What they do is not a massive undertaking," said Hania Zlotnik, chief of population estimates and projections of the Population Division of the United Nations. "Our assumptions are getting more complicated all the time because there is more variability on how the different countries' fertility transition to lower fertility."